"Original sin," says Diarmaid MacCulloch, Professor of the History of the Church at the University of Oxford, "is one of the more plausible concepts" of Christian doctrine, for it corresponds all too well with our experience of this squalid, postlapsarian world. It is at the very heart of the faith, or perhaps one ought to say "base", because upon it are the sprawling, stupefying superstructures of atonement, redemption, salvation and damnation built.

But the idea of original sin has resonance elsewhere too, in the history of nations: it gives shape, direction and impetus to history. United States President Barack Obama, in his acclaimed speech on race in March 2008, was repeating a familiar trope when he spoke of the Declaration of Independence as being "stained by this nation's original sin of slavery." For if a nation starts blemished by sin, then its history must be seen as an atoning for this sin, as one long, pining search for salvation. It speaks to the American belief in perfectibility: the process of history is one of ongoing refinement. After all, what was that speech called? "A More Perfect Union" – taken out of the first line of the preamble to the Constitution.

Moving south to Mexico, Nobel Prize laureate Octavio Paz tells us that the original sin in his country is the Spanish Conquest, the one scarifying beginning-and-end-in-one that so indelibly marks the history of Mexico:

The symbol of this violation is doña Malinche, the mistress of Cortés. It is true that she gave herself voluntarily to the conquistador, but he forgot her as soon as her usefulness was over… as a small boy will not forgive his mother if she abandons him to search for his father, the Mexican people have not forgiven La Malinche for her betrayal.

Mexican history, therefore, is a chance to overcome this bastard inheritance. The Old World, with its facade of venerable, bloodless antiquity, seems not to be riven with these particular urgings of the conscience. Perhaps once, after the Norman Conquest in 1066, whole generations of learned Englishmen were horrendously conflicted about speaking French while everyone else spoke plain old Anglo-Saxon. (And how on earth did they cope without postcolonial theories and concepts like "hybridity"?) And we often forget that Italy and Germany were only forged in the wars of the second half of the 19th century. But now it seems that having to wrestle with original sin is the birthright of new nations, like so many other agonies. These agonies are familiar to us Singaporeans: questions of identity, culture, language and authenticity. But what, then, is Singapore's original sin?

Colonisation is not the answer, though this isn't because of British benevolence. The empire was essentially a global drug cartel, the result of a bid to balance the account books by getting millions of Chinese workers – not only in China, but in Singapore and the surrounding region as well – addicted to opium. But the trauma was not grievous enough, it seems. S. Rajaratnam, our first Culture and Foreign minister before he became Deputy Prime Minister, said to the ruling People's Action Party (PAP) faithful in 1969 that: "We started off as an anti-colonial party. We have passed that stage: only Raffles remains." We do not know the tone he said it in; we can only hope it was a slightly shamefaced irony. So implausibly, "Raffles" is now a mark of excellence. We dislodged him from the Raffles Museum and the Raffles Library, but have lodged him elsewhere and all over, in at least one shopping centre and one town club.

So what else? Separation from Malaysia, our inglorious expulsion from the Federation, was traumatic, especially for those who believed in a Malay(si)an nation. The idea of merger has not been entirely exorcised, of course: Lee Kuan Yew spoke of the possibility of re-merger as recently as in October 2007. But very few now would think of separation as something to be reversed. It would, perversely, mean that Singapore's history would be little more than a deviating blip from the original course.

The more provocative of us might pick Operation Cold Store, a massive detention operation launched in Singapore on February 2, 1963, which rounded up supposed communist subversives, including Lim Chin Siong, Fong Swee Suan, S. Woodhull and James Puthucheary. In doing so, the PAP also effectively crippled the breakaway leftist faction that formed the opposition Barisan Sosialis in 1961. The history of this still needs sorting through, and time will perhaps bring objectivity and clarity. But in it, we can see the outlines of what would become the heavy hand of the PAP. This pick would be tendentious, divisive and, above all, untrue to the spirit of the question. But these episodes provide a clue. The circumstances of Singapore's creation meant that Singapore was a very deliberate construction. The sense of crisis meant that nearly everything could be called upon for sacrifice to the greater good of nation-building.

It is again S. Rajaratnam, the most erudite and thoughtful of the PAP Old Guard, who in his many pronouncements on culture – when read together – reveals what this original sin may be. As Minister for Culture, he was aware of the vertigo-inducing sense of having to start from nothing. His critics asked him, when he took office, what a common Singaporean (or in those days, "Malayan") culture meant. It was a culture, he replied, that would have "new beliefs and social behaviour… common to all [ethnic] communities." It would be a new consciousness, a new identity, a new way of being, based on a history as yet unwritten. But to be Singaporean was above all, an act of faith, he said in 1960:

We must first accept the premise that it is an act of faith… We must believe we can do it soon and that we can do it by a deliberate act of will.

After retirement, he still held this sense that identity was a deliberate willing-to-be, a conscious act of convicted faith, that "being a Singaporean… is conviction and choice." We cannot underestimate the enormity of Rajaratnam's task, because it was simply impossible. As he himself realised, "culture is not a statue or a chair." But part of the premise of this common culture was a collective forgetting, what Rajaratnam would later call a "collective selective amnesia". He went on to say: "Being a Singaporean means forgetting all that stands in the way of one's Singaporean commitment."

One can read his comments more charitably in the light of fears of communalism, the fear that pre-colonial history could be used to make ethnic claims of priority and privilege. But this assumed dispensability and, ultimately, worthlessness of memory, along with a very deliberate sense of contrivance, is nonetheless emblematic of the ruling party's approach. This unusually generous dispensation granted to all Singaporeans, that it is acceptable to forget at almost any cost – that is our most heinous original sin. It was this belief, as one of our poets had perceptively said, that "there is no future in nostalgia" (Arthur Yap). Yes, nations are built on collective selective amnesia. But they are not built on an almost total blankness of mind. Thus at the very moment in which we began to write our history, our pens were confiscated from us and we were told to face the blackboard.

And so we forgot. We forgot that some places once existed. We forgot that the Chinese arrived here speaking a mad cacophony of dialects, some more mutually intelligible to others than the rest. Instead, we engineered it so that all would utter the tyrannical dialect of Beijing. We forgot about the political detainees on our island – or, more accurately, on Sentosa. We forgot about the significance of that "crownless Prince of Palembang" (from Alfian Sa'at's poem, 'Singapore you are not my Country'), the fact that we once dreamt of a pan-Malayan ideal because we are, like it or not, part of a larger Malay world. We were not told of this historic canvas. Raffles himself said about Singapore's significance:

In the minds of the natives it [Singapore] will always be associated with their fondest recollections, as the seat of their ancient government… The advantage of selecting a place thus hallowed by the ideas of a remote antiquity, and the veneration attached to its ancient line of kings, from whom they are still proud to trace their descent, must be obvious.

We were told to forget, in certain company, that our tongues are used to a native brand of English, itself a wonderful and unique historical creation. (The result: a wide sampler platter of fake American and fake British.) The ruling party, when it finally sensed the damage this had caused, suggested "Asian values" and "Confucianism". If anything, this staged retrieval of our supposed ancestral roots was a betrayal of Rajaratnam's own vision of a common culture. And as we forgot, a single cast-iron narrative was forged. Instead of a work of many hands, the Singapore story often became the script of one tight-fisted director.

The ultimate irony hit when the Old Guard started to die off. Rajaratnam died in 2006, Goh Keng Swee in 2010, Toh Chin Chye in 2012. Some of the older generation could recall their personalities and contributions. But many young Singaporeans have not heard of them. They are not aware that Rajaratnam wrote the pledge, for one, and that Goh Keng Swee made pioneering and completely vital contributions to areas as diverse as defence, education and the economy. And from the book Men in White: The Untold Story of Singapore's Ruling Political Party (Straits Times Press, 2010), we were only recently told that Toh cast the deciding vote in a PAP central executive committee meeting in 1959 that made Lee Kuan Yew – instead of the city mayor, Ong Eng Guan – Prime Minister. We paid our respects, lamented that so few knew, and then went on with our lives. In the unbelievably narrow conception of the Singapore story, even these great men are jostling for room for theirs to be told.

Singapore will celebrate its 50th year of independence in 2015. The salvation, the cure for original sin, is right before our eyes: this very nearly half-century of history. To the ever-present question of "What does it mean to be Singaporean?" (another new world privilege, it seems), the answer should simply be, "to be part of a country which has had this 50-year history, a lot of it unwritten." There are still all manner of political, social and intellectual histories to be written and recorded. The elderly among us today are untapped storehouses of memory. Places and monuments that have vanished can be reanimated in writing. In doing so, we might find a part of Singapore – in the past, present or the imaginary – that will remain forever meaningful.

Rajaratnam was right about Singaporean-ness being a deliberate act of the will. If we are serious about being Singaporeans, then let us collectively channel this will to revoke this dispensation to forget. Let us reexamine the events of the past that we have allowed to linger like foul miasma, poisoning the body politic. Let those in power not hinder us, but help us, by giving us access to the resources we need.

This call for many stories, for multiple voices, for more remembering and less forgetting, is not new at all – many of our writers and poets have made it too. But perhaps, the call is more urgent as we age, as more of the past is being irretrievably forgotten. Jorge Luis Borges wrote of Argentina that "precisely because it is a new country, there is a strong feeling for time." We have blunted our natural sensitivity to history. It is now time to feel our way back to it, while our nation is yet young.